Water-dispersible adhesive composition and process

ABSTRACT

Disclosed is a water-dissipatable or dispersible adhesive composition that is useful in forming paper articles and other products that can be recycled through repulping in both neutral and alkaline media. The water-dispersible adhesive composition is preferably a hot melt adhesive that is a low molecular weight, branched copolyester containing a sulfomonomer. Additional utility for the invention resides in the manufacture of recyclable articles where insolubility in body fluids combined with solubility in tap water are required.

This application is a continuation-in-part of application Ser. No.175,330 filed Dec. 29, 1993, now abandoned.

FIELD OF THE INVENTION

The present invention is directed to a water-dispersible adhesivecomposition. More particularly, the present invention is directed to ahot melt adhesive composition that, due to its water-dispersibility, isrepulpable, allowing paper products, nonwoven assemblies, and otherdisposable products to be more effectively recycled. The presentinvention is also directed to a hot melt adhesive composition containingpolyester that is water dispersible while maintaining excellent adhesiveproperties.

BACKGROUND OF THE INVENTION

Many adhesives including hot melt adhesives are useful for bondingvarious substrates together such as wood, paper, plastics, and textiles,as well as other materials. One use for which hot melt adhesives arewell suited is the fabrication of corrugated paper board. Hot meltadhesives, useful for producing corrugated paper board, must have highbond strength under conditions of shock, stress, high humidity, andextremes of temperature encountered in transportation and storage. Inaddition, the melt point, wetting time, initial tack, setting time, potlife, and general handling qualities on automatic corrugated boardmachinery are essential considerations.

At present, it is very desirable to recycle paper, paper products, andother disposable products to conserve material resources and to avoidlarge additions to landfill space. It is thus a general practice in thepaper industry to recover the used and waste corrugated material andrepulp the material for use in the preparation of other materials suchas cardboard. The use of polyolefin hot melt adhesives to close or sealcartons made from corrugated material has presented problems in regardto repulpability of the used boxes or cartons (see U.S. Pat. Nos.4,070,316; 4,127,619; 4,146,521; 4,460,728; 4,471,086; and 4,886,853).In fact, all the presently available hot melt and pressure sensitiveadhesives are largely water insoluble and very difficult to disperseduring the repulping process. This fact makes certain paper products, inwhich adhesives are necessarily utilized, unattractive since failure todisperse the insoluble adhesives results in lower quality recycled paperhaving variable composition and nonuniformity and thus, lower productvalue.

One approach to avoid the presence of insoluble adhesives in therecycled paper products is to use adhesives whose density is differentfrom the density of water and pulp in water, thus permittinggravitational separation. However, this requires separation steps whichcan increase the recycling costs of the paper products containingadhesives.

Another approach could be to use a water soluble adhesive that would beseparated from the pulp and dispersed into the water during repulping.This type of adhesive would remain in the water when the pulp isrecovered. However, presently available water soluble or dispersibleadhesives are "natural" adhesives such as dextrins, cellulose gums, andanimal glues derived from the hides and bones of animals and theseadhesives have lower strength, fail to adhere well to paper and woodstocks with coatings or heavy ink applications, and sometimes requirespecial treatment and handling because of their high viscosity.Therefore, the use of these adhesives, while being easily recyclable, isquite low due to poor adhesive characteristics. Attempts to producesynthetic water-dispersible hot melt adhesive compositions haveheretofore been unsuccessful due to resulting poor adhesive propertiessuch as thermal stability, low strength, poor viscosities and low coldflow resistance. Additionally, costs and ease in manufacturing haveprecluded their use (see U.S. Pat. Nos. 3,919,176 and 5,098,962).

In addition to paper and paper products, there are many disposableproducts, such as diapers, in which hot melt adhesives are used. The useof current hot melt adhesives in these products complicate attempts torecycle products and separate out the insoluble sticky hot meltadhesives.

In light of the above, it would be very desirable to produce awater-dispersible adhesive, particularly a hot melt adhesive, atreasonable costs that maintains the desirable properties of presentlyavailable adhesives.

SUMMARY OF THE INVENTION

The water-dispersible adhesive composition according to the presentinvention comprises a branched water-dispersible polyester compositionmade of the residues or moieties of reaction products;

(I) at least one difunctional dicarboxylic acid which is not asulfomonomer;

(II) about 2 to 15 mol percent, based on the total of all acid, hydroxyland amino equivalence, of residues of at least one difunctionalsulfomonomer containing at least one sulfonate group bonded to anaromatic ring wherein the functional groups are hydroxyl, carboxyl, oramino;

(III) at least one diol or a mixture of a diol and a diamine comprising:

(A) about 0.1 to 85 mol percent, based on the total mol percent of diolmoieties or diol and diamine moieties, of a diol or diamine having theformula H(--OCH₂ CH₂ --)_(n) OH and HRN(.paren open-st.CH₂ CH₂ O .parenclose-st.)_(n) NHR wherein n is 2 to about 20 and R is hydrogen or C₁-C₆ alkyl provided that the mol percent of such moieties is inverselyproportional to the value of n;

(B) about 0.1 to 15 mol percent, based on the total mol percent of diolmoieties or diol and diamine moieties, of moieties of a poly(ethyleneglycol) having the formula H(--OCH₂ CH₂ --)_(n) OH wherein n is 2 toabout 500, provided that the mol percent of such moieties is inverselyproportional to the value of n; and

(C) 0 to greater than about 99 mol percent of the diol component or dioland diamine mixture being selected from the group consisting of a glycoland a mixture of glycol and diamine having two --NRH groups, the glycolcontaining two --C(R¹)₂ --OH groups wherein R¹ in the reactant is ahydrogen atom, an alkyl of 1 to 5 carbon atoms, or an aryl group of 6 to10 carbon atoms;

(IV) 0 to about 40 mol % of a difunctional monomer reactant selectedfrom the group consisting of hydroxycarboxylic acids having one--C(R--)₂ --OH group, aminocarboxylic acids having one --NRH group,aminoalkanols having one --C(R--)₂ OH group and one --NRH group andmixtures of said difunctional reactants wherein R in the reactant ishydrogen or an alkyl group of 1 to 6 carbon atoms; and

(v) about 0.1 to 40 mol % of a "multifunctional" or "branch-inducing"reactant containing at least three functional groups selected fromhydroxyl, carboxyl, amino, and mixtures thereof;

the polymer containing substantially equal mol proportions of acidequivalents (100 mol %) and diol or diol and diamine equivalents (100mol %) wherein at least 20 weight percent of the groups linking themoieties of the monomeric units are ester linkages and wherein theinherent viscosity is at least 0.1 dL/g measured in a 60/40 parts byweight solution of phenol/tetrachloroethane at 25° C. and at aconcentration of about 0.25 g of polymer in 100 ml of the solvent, theglass transition temperature T_(g) is no greater than 20° C., and thering and ball softening point is at least 70° C. Alternatively, thewater-dispersible adhesive composition according to the presentinvention can be a blend of two different polyesters that comprises:

(1) about 20 to 80 weight percent of the linear water-dispersiblepolyester composition made of the residues or moieties of reactionproducts;

(i) at least one difunctional dicarboxylic acid which is not asulfomonomer;

(ii) about 4 to 25 mol percent, based on the total of all acid, hydroxyland amino equivalence, of residues of at least one difunctionalsulfomonomer containing at least one sulfonate group bonded to anaromatic ring wherein the functional groups are hydroxyl, carboxyl, oramino;

(iii) at least one diol or a mixture of a diol and a diamine comprising:

(A) at least 15 mol percent, based on the total mol percent of diolmoieties or diol and diamine moieties, of a diol or diamine having theformula H(--OCH₂ CH₂ --)_(n) OH and HRN.paren open-st.CH₂ CH₂ O.parenclose-st._(n) NHR wherein n is 2 to about 20 and R is hydrogen or C₁ -C₆alkyl,

(B) about 0.1 to less than about 15 mol percent, based on the total molpercent of diol moieties or diol and diamine moieties, of moieties of apoly(ethylene glycol) having the formula H(--CH₂ CH₂ --)_(n) OH whereinn is 2 to about 500, provided that the mol percent of such moieties isinversely proportional to the value of n; and,

(iv) 0 to about 40 mol percent moieties of a difunctional monomerreactant selected from hydroxycarboxylic acids, aminocarboxylic acidsand aminoalkanols; the polymer containing substantially equal molproportions of acid equivalents (100 mol %) and diol or diol and diamineequivalents (100 mol %) wherein at least 20 weight percent of the groupslinking the moieties of the monomeric units are ester linkages andwherein the inherent viscosity is at least 0.1 dL/g measured in a 60/40parts by weight solution of phenol/tetrachloroethane at 25° C. and at aconcentration of about 0.25 g of polymer in 100 ml of the solvent; and

(2) about 20 to 80 weight percent of the branched water-dispersiblepolyester made of the moieties of reaction products;

(a) at least one difunctional dicarboxylic acid which is not asulfomonomer;

(b) about one to 20 mol percent, based on the total of acid, hydroxyland amino equivalents, of residues of at least one difunctionalsulfomonomer containing at least one sulfonate group bonded to anaromatic ring wherein the functional groups are hydroxyl, carboxyl, oramino;

(c) at least one difunctional reactant selected from a glycol or amixture of glycol and diamine having two --NRH groups, the glycolcontaining two --C(R¹)₂ --OH groups wherein R in the reactant ishydrogen or an alkyl group of 1 to 6 carbon atoms, and R¹ in thereactant is a hydrogen atom, an alkyl of 1 to 5 carbon atoms, or an arylgroup of 6 to 10 carbon atoms;

(d) 0 to about 40 mol % of a difunctional reactant selected fromhydroxycarboxylic acids having one --C(R--)₂ --OH group, aminocarboxylicacids having one --NRH group, amino-alcohols having one --C(R--)₂ --OHgroup and one --NRH group, or mixtures of said difunctional reactantswherein R in the reactant is hydrogen or an alkyl group of 1 to 6 carbonatoms; and

(e) 1 to 40 mol % of a "multifunctional" or "branch-inducing" reactantcontaining at least three functional groups selected from hydroxyl,carboxyl, amino, and mixtures thereof;

wherein all stated mol percents are based on the total of all acid,hydroxyl, and amino group containing reactants being equal to 200 molpercent, and wherein the polymer containing a portion of the acid-groupcontaining reactants (100 mol percent acid) to hydroxyl and amino-groupcontaining reactants (100 mol %).

The present invention also further comprises a process of applying theabove water-dispersible adhesive composition between two substrates toform a laminate. The adhesive can later be separated from the substratesin recycling by repulping the entire laminate structure. This inventioncomprises applying the above water-dispersible adhesive composition inliquid form to a surface of a substrate and, while remaining in theliquid form, applying a second surface of a substrate to thewater-dispersible adhesive composition thereby forming an article ofmanufacture that comprises the water-dispersible adhesive compositionlaminated between two substrates or two surfaces of a substrate.

The present invention also comprises the bonded articles of manufacturehaving the adhesive composition between two substrates such as in cartonsealings, corrugated board and diaper construction.

DETAILED DESCRIPTION OF THE INVENTION

The applicants have unexpectedly discovered an improved adhesivecomposition that can be applied as a liquid dispersion (aqueous orsolvent) on substrates as well as by hot melt application. The inventiveadhesive composition not only has good aqueous adhesive properties butalso has excellent hot melt adhesive properties and is totallyrecyclable when the products containing the adhesive are recycled byrepulping. The present adhesive composition is easily repulpable andremoved from the fibers from paper or wood pulp used in disposableproducts, particularly in the preferred hot melt applications. Theadhesive according to the present invention permits recycling ofdisposable products at significantly reduced processing costs withoutaffecting the physical properties of the adhesive and resulting article.

Certain water-dispersible polyester compositions are described in detailin U.S. Pat. Nos. 3,734,874; 3,779,993; 4,233,196; and 4,335,220, thedisclosures of which are incorporated herein by reference in theirentirety.

The water-dispersible adhesive composition according to the presentinvention that can be a single polyester is a branched water-dispersiblepolyester made of the residues or moieties of reaction products; (I);(II); (III); (IV) and (V) above.

Alternatively, the water-dispersible adhesive composition according tothe present invention is a blend of two different polyesters thatcomprises: (1) about 20 to 80 weight percent of the linearwater-dispersible polyester composition made of the residues or moietiesof reaction products; (i); (ii); (iii); and (iv) above and (2) about 20to 80 weight percent of the branched water-dispersible polyester made ofthe moieties of reaction products; (a); (b); (c); (d); and (e) above.

Although the inventive single polyester water-dispersible adhesivecomposition and the inventive water-dispersible adhesive compositionthat is a blend of two different polyesters have different amounts ofmonomers and a different mix of groups of monomers, some specific groupsof suitable monomers and preferred monomers of these groups are the sameas is illustrated below.

The sulfonate-containing, water-dispersible, adhesives and polyesters ofthis invention comprise polyesters, including polyesteramides, havingrepeating, alternating residues or moieties of one or more dicarboxylicacid which is not a sulfomonomer and one or more diols or a combinationof one or more diols and one or more diamines wherein the molpercentages are based on 100 mol percent dicarboxylic acid residues and100 mol percent diol or diol and diamine residues, for a total of 200mol percent. Alternatively, the polyesters can include residues ofmonomers having mixed functionality such as hydroxycarboxylic acids,aminocarboxylic acids and/or aminoalkanols.

Examples of suitable difunctional dicarboxylic acid monomers used tomake the residue of (I), (i), and (a) include aliphatic dicarboxylicacids, alicyclic dicarboxylic acids, aromatic dicarboxylic acids, ormixtures of two or more of these acids. Examples of preferred suitabledicarboxylic acids include succinic; glutaric; adipic; azelaic; sebacic;fumaric; maleic; itaconic; 1,4-cyclohexanedicarboxylic;1,3-cyclohexanedicarboxylic; phthalic; terephthalic; and isophthalic. Ifterephthalic acid is used as the dicarboxylic acid component of thepolyester, superior results are achieved when at least 5 mol percent ofone of the other acids is also used. It should be understood that theuse of the corresponding acid anhydrides, esters, and acid chlorides ofthese acids is included in the term "dicarboxylic acid".

The difunctional sulfo-monomer component of (II), (ii), and (b) ispreferably a dicarboxylic acid or ester thereof containing a metalsulfonate group or a glycol containing a metal sulfonate group or ahydroxy acid containing metal sulfonate group. The cation of thesulfonate salt can be NH₄ ⁺, or the metal ions Li⁺, Na⁺, K⁺, Mg⁺⁺, Ca⁺⁺,Cu⁺⁺, Ni⁺⁺, Fe⁺⁺, Fe⁺⁺⁺ and the like.

Residue or reactant (II), (ii), and (b) in the polyester of the presentinvention is a difunctional monomer containing a --SO₃ M group attachedto an aromatic nucleus, wherein M is hydrogen NH₄ ⁺, or a metal ion. Thedifunctional monomer component may be either a dicarboxylic acid or adiol adduct containing a --SO₃ M group. The cation of the sulfonate saltgroup can be NH₄ ⁺, or the metal ions Li⁺, Na⁺, K⁺, Mg⁺⁺, Ca⁺⁺, Cu⁺⁺,Ni⁺⁺, Fe⁺⁺, Fe⁺⁺⁺ and the like. Preferred are monovalent cations, suchas NH₄ ⁺, Li⁺, Na⁺, and K⁺, when stability in water is desired.

The --SO₃ M group is attached to an aromatic nucleus, examples of whichinclude benzene, naphthalene, anthracene, diphenyl, oxydiphenyl,sulfonyldiphenyl, and methylenediphenyl.

The cationic portion of a nonmetallic sulfonate group optionally presentin reactant (II), (ii), and (b) is a nitrogen-based cation derived fromnitrogen-containing bases which may be aliphatic, cycloaliphatic oraromatic basic compounds that have ionization constants in water at 25°C. of 10⁻³ to 10⁻¹⁰ preferably 10⁻⁵ to 10⁻⁸. Especially preferrednitrogen-containing bases are ammonia, dimethylethanolamine,diethanolamine, triethanolamine, pyridine, morpholine, and piperidine,due to availability, cost, and usefulness. Such nitrogen-containingbases and cations derived therefrom are described in U.S. Pat. No.4,304,901, the disclosure of which is incorporated herein by referencein its entirety.

It is preferred that reactant (II) be present in a concentration ofabout 4 to 12 mol percent, more preferably about 6 to 10 mol percent,with a mol percent of about 8 being most preferred based on total acidequivalents. At amounts below 4 mol percent the polyester is lessrepulpable whereas at amounts above 12 mol percent the polyester is alittle too water-sensitive.

It is preferred that reactant (ii) and, independently, reactant (b) bepresent in an amount of 2 to 25 mol percent, more preferably about 4 to15 mol percent, based on the total acid equivalents.

Examples of preferred diols of (III) (A) and (iii) (A), due toavailability, include diethylene glycol, triethylene glycol, andmixtures thereof. The preferred concentration of (III) (A) is about 10to 80 mol percent, however, when these are the preferred diols of (III)(A) the concentration is about 20 to 80 mol percent. At amounts outsidethis range of 20 to 80 the polyesters have lower softening points andhigher Tg than what is most desired.

The moieties of (III) (A) and (iii) (A) can be the same as (III) (B) and(iii) (B), respectively, when the value n is low. However, it ispreferred that (B) be a different moiety and be a poly(ethylene glycol).Examples of suitable poly(ethylene glycols) of (III) (B) and (iii) (B)include relatively high molecular weight polyethylene glycols, some ofwhich are available commercially under the designation "Carbowax", aproduct of Union Carbide. Poly(ethylene glycols) having molecularweights of from about 500 to about 5000 are especially suitable.

The moieties of (B) are preferably at a concentration of about 1 to 5mol percent, particularly when n is 10 to 30, due to the preferablyhigher softening points. The remaining portion of the glycol componentof (III), (iii), and (c) can consist of aliphatic, alicyclic, andaralkyl glycols. Examples of these glycols include neopentyl glycol;ethylene glycol; propylene glycol; 1,3-propanediol;2,4-dimethyl-2-ethylhexane-1,3-diol; 2,2-dimethyl-1,3-propanediol;2-ethyl-2-butyl-1,3-propanediol; 2-ethyl-2-isobutyl-1,3-propanediol;1,3-butanediol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol;2,2,4-trimethyl-1,6-hexanediol; thiodiethanol;1,2-cyclohexanedimethanol; 1,3-cyclohexanedimethanol;1,4-cyclohexanedimethanol; 2,2,4,4-tetramethyl-1,3-cyclobutanediol;p-xylylenediol and neopentyl glycol. Copolymers may be prepared from twoor more of the above glycols. Preferred glycols, due to availability,cost, and usefulness, include neopentyl glycol, ethylene glycol,1,3-propane diol, 1,4-butane diol, 1,6-hexane diol and cyclohexanedimethanols.

Advantageous examples of difunctional monomer component of (III) and (c)which are diamines include ethylenediamine; hexamethylenediamine;2,2,4-trimethylhexamethylenediamine; 4-oxaheptane-1,4-diamine,4,7-dioxadecane-1,10-diamine; 1,4-cyclohexanebismethylamine;1,3-cyclohexanebismethylamine; heptamethylenediamine;dodecamethylenediamine, etc.

The amount of the moieties III (C) present in the polyester ispreferably a minor amount up to about 99 mol percent, more preferably 20to 80 mol percent with a mol percent of about 30 to 70 being morepreferred due to the preferred balance between the desired low Tg andthe desired high softening point.

Advantageous difunctional components which are aminoalcohols oraminoalkanols include aromatic, aliphatic, heterocyclic, and other typesin regard to component (IV), (iv) and (d). Specific examples include5-aminopentanol-1,4-aminomethylcyclohexanemethanol,5-amino-2-ethyl-pentanol-1, 2-(4-β-hydroxyethoxyphenyl)-1-aminoethane,3-amino-2,2-dimethylpropanol, hydroxyethylamine, etc. Generally theseaminoalcohols contain from 2 to 20 carbon atoms, one --NRH group and one--CR₂ --OH group.

Advantageous difunctional monomer components which are aminocarboxylicacids include aromatic, aliphatic, heterocyclic, and other types inregard to component (IV), (iv), and (d) and include lactams. Specificexamples include 6-aminocaproic acid, its lactam known as caprolactam,omega aminoundecanoic acid, 3-amino-2-dimethylpropionic acid,4-(β-aminoethyl)benzoic acid, 2-(β-aminopropoxy)benzoic acid,4-aminomethylcyclohexanecarboxylic acid,2-(β-aminopropoxy)cyclohexanecarboxylic acid, etc. Generally, thesecompounds contain from 2 to 20 carbon atoms.

These moieties (IV) (iv) and (d) are less preferred, due to cost andperformance, but they can be present. The concentration of thesemoieties is preferably below 20 mol percent, more preferably below 10mol percent, including zero.

Preferred water dispersible linear polyesters of (1) in the polyesterblend contain diacid monomer residues that are about 75 to 90 molpercent isophthalic acid residues, and about 10 to 25 mol percent5-sodiosulfoisophthalic acid monomer residues; and diol monomer residuesof about 45 to 100 mol percent diethylene glycol monomer residues and 0up to 55 mol percent 1,4-cyclohexanedimethanol.

The more preferred water dispersible linear polyesters of (1) have aninherent viscosity of 0.1 to 0.6, preferably 0.2 to 0.5, and a Tg rangeof about 25° to 88° C., preferably about 29° to 55° C.

The branched water dispersible polyester of (2) is made of the moietiesof the reaction products (a), (b), (c), (d), and (e) above.

Related branched water-dispersible polyesters of (2) above are disclosedin U.S. Pat. No. 5,218,042, the disclosure of which is incorporatedherein by reference in its entirety. U.S. Pat. No. 5,218,042 is directedtowards increasing the stability of dispersions in water and thusendcaps the acid groups or forms a diol adduct of a dicarboxylicsulfomonomer to maintain dispersion stability. However, the presentinventive compositions are not directed towards maintaining a stableemulsion, simply producing an emulsion by pulping and dissolving thehot-melt adhesive in water until it is separated from the fibers.Therefore, endcapping and forming a diol adduct of the sulfomonomer isnot a requirement for the present invention.

The polyester compositions are branched by virtue of the presence of amultifunctional reactant (V) and (e) that contains at least threefunctional groups selected from hydroxyl, carboxyl, and amino. Examplesof preferred multifunctional reactants of (V) and (e) aretrimethylpropane (TMP), trimethylolethane (TME), glycerine,pentaerythritol, erythritol, threitol, dipentaerythritol, sorbitol,trimellitic anhydride, pyromellitic dianhydride, and dimethylolpropionicacid with TMP being most preferred, due to availability and effectiveresults.

The amount of this branching agent (V) and (e) is preferably below 20mol percent, more preferably below 10 mol percent, (including the rangefor (V) of 0.5 to 10), with a concentration of about 1 to 7 or 2 to 6mol percent being most preferred. At very high amounts of branchingagent the polyester is prone to gelation whereas at low amounts, such asbelow 0.5 and 0.1, the polyester has poorer performance and properties.

The dispersible linear polyester composition of (1) is blended with thebranched water-dispersible polyester composition of (2) at temperaturesgreater than 200° C., preferably about 225° C., for at least one hour.In the adhesive blend composition according to the present invention therelative amounts of the two polyesters vary from about 20 to 80 weightpercent of the polyester of (1) and about 20 to 80 weight percent of thepolyester of (2). The concentration of these two polyesters in the hotmelt adhesive composition according to the present invention ispreferably greater than 30 but less than 80 weight percent polyester of(1) and greater than 20 but less than 70 weight percent of the polyesterof (2). The concentration of the two polyesters is more preferably about40 to 77 weight percent (1) and about 23 to 60 weight percent of (2),even more preferably about 60 to 75 weight percent of (1) and about 25to 40 weight percent of (2) with a concentration of the two polyestersin weight percent of about 70 (1) and about 30 (2) being most preferred.Higher amounts of the polyester of (1) increase the melting point of thefinal adhesive composition. At amounts of the polyester of (1) higherthat 80 weight percent, the adhesive has too high of a melting point tobe practical. Higher amounts of the polyester of (2) decrease themelting point of the final adhesive. At amounts of the polyester of (2)higher that 80 weight percent, sometimes higher than 70, the adhesivehas too low of a melting point to be practical.

The polyesters according to the present invention preferably have atleast 50 weight percent of the linking groups linking the moieties ofthe monomeric units being ester linkages, more preferably at least 90weight percent, with an ester linkage weight percent of 100 being mostpreferred.

The water-dispersible polyesters described herein have an inherentviscosity of at least 0.1 dL/g, preferably about 0.2 to 0.5 dL/g,measured in a 60/40 parts by weight solution of phenol/tetrachloroethaneat 25° C. and at a concentration of about 0.25 g of polymer in 100 ml ofsolvent.

The final adhesive compositions preferably have a number averagemolecular weight of about 2,000 to 20,000 more preferably about 3,000 to10,000. Although it is desirable to have as high a molecular weight aspossible to achieve the maximum physical properties, such as tensilestrength and peel strength, the melt viscosity also increase asmolecular weight increases. Therefore, at very high molecular weightsthe melt viscosity is too high for many useful applications.

The preferred Tg of the adhesive composition according to the presentinvention is below 10° C. and more preferably varies from about 4° to-20° C., with a Tg of about 4° to -13° C. being most preferred. The Tg(glass transition temperature) of the adhesive compositions of thepresent invention are preferably as low as possible. Thus Tgs below 4°C. and even below 0° C. are preferred. Tgs of greater than 0° C. havegenerally higher ring and ball softening point (RBSP) and heatresistance but are not as flexible. A low Tg means that the adhesivecompositions will not be brittle, thus, cartons adhered together withthe adhesive compositions of the present invention when impacted, evenat extremely cold temperatures will not shatter and thus maintainadhesion. However, extremely low Tgs are not easily obtained or at leastnot easily obtained without greatly affecting some other property, suchas lowering the ring and ball softening point.

The hot melt adhesive composition according to the present inventionpreferably has a viscosity of about 1,500 to about 30,000 centipoise at350° F. (177° C.), more preferably about 3,000 to 15,000 cP at 350° F.(177° C.) due to ease in application.

The ring and ball softening point (RBSP) of the adhesive composition ofthe present invention is preferably at least 80° C., more preferably 80°to 100° C. The high temperatures of RBSP are better since this means athigher storage temperatures delamination will not occur. (High RBSPprovides delamination resistance).

The adhesive compositions according to the present invention areparticularly useful due to their good combination of properties and aresuitable for use as adhesives for many substrates including non wovenassemblies (such as non woven polypropylene), paper products (such aspaper and paperboard), and wood pulp and are easily recyclable andrepulpable. The hot melt adhesives according to the present inventionare recyclable/repulpable and improved over prior art repulpable hotmelt adhesive compositions in that the set time, temperaturesensitivity, compatibility, stability on storage, shear strength,tensile strength, viscosity, and cold flow resistance are improved.

The adhesive composition according to the present invention is appliedto one substrate with a second substrate being placed on top of theadhesive forming an article having the adhesive laminated between twosubstrates.

The adhesive composition according to the present invention can beapplied in liquid form in solvent or in an aqueous solution at aconcentration of about 10 to 70 weight percent with the remainder beingsolvent or water or mixtures thereof. Surfactants and other additivescan also be present to aid in the dispersibility of the adhesivecomposition. When applied as a solution, the adhesive compositions aregenerally applied by conventional processes, such as extrusion coating,spray coating, roll coating, brush coating, dip coating, etc.

The adhesive composition according to the present invention ispreferably used as a hot melt adhesive. The hot melt adhesivecomposition is preferably applied in the melt at a temperature of about150° to 200° C. to a surface of a substrate and, while remaining moltenand pliable, applying a second surface of a substrate to thewater-dispersible hot melt adhesive composition thereby forming anarticle of manufacture that comprises the water-dispersible hot meltadhesive composition laminated between two substrates or two surfaces ofa substrate.

The adhesive compositions of the present invention are preferably notcrosslinked since that would impair their water dispersibility andrepulpability. However, they could be crosslinked, to a certain extentwith diisocyanates to improve strength and heat resistance although thisis less preferred.

The adhesive composition according to the present invention can alsocontain standard additives including stabilizers, preferably about 0.1to about 0.5 weight percent stabilizers. Suitable stabilizers includethe antioxidant type and generally consist of sterically hinderedphenols, or sulfur or phosphorous substituted phenols. An especiallyuseful antioxidant is Irganox 1010 (from Ciba-Geigy, Hawthorne, N.Y.)which is a pentaerythritoltetrakis-3(3,5-di-tertiarybutyl-4-hydroxyphenyl)propionate.

Additional additives can be added to raise and lower Tg and RBSP. Theseinclude, for example, elastomers, plasticizers, low molecular weightpolyolefins, resins, and tackifiers. Although, elastomers can be addedto the polyester composition, the presence of such elastomers may beadverse to certain desired properties of the composition. Therefore, itis preferable that the composition of the present invention containsubstantially no elastomer. Additionally, the plasticizers such as DOP,DOTP, phenols, glycols, phthalate esters and the like that can be added,can distract from the heat resistance of the final composition loweringthe RBSP.

Other additives such as UV light absorbers, nucleating agents,colorants, pigments, solvents, and fillers can be present in smallamounts as needed and known in the adhesive art.

Tackifiers are added to the polyester composition to prevent cold flowand increase the softening point. Tackifiers are typically selected fromat least one of the groups consisting of hydrocarbon resins, syntheticpolyterpenes, functional copolymers, and rosin esters. Hydrocarbonresins are disclosed in U.S. Pat. No. 3,850,858 and functionalcopolymers, such as styrene-co-maleic anhydride, are well known in theart. Hydrocarbon resins, prepared according to U.S. Pat. No. 3,701,760,polyterpenes, and rosin esters can be used alone or in combinations.These tackifying resins, which preferably have softening points of atleast 100° C. and most preferably 120° C., can be used in amounts ofabout 10% to 50% by weight of the adhesive composition, preferably about25% to about 40% by weight. Suitable resins and rosin esters are theterpene polymers having a suitable ring and ball softening point such asthe polymeric, resinous materials including the dimers as well as higherpolymers obtained by polymerization and/or copolymerization of terpenehydrocarbons such as the alicyclic, monocyclic, and bicyclicmonoterpenes and their mixtures, including allo-ocimene, carene,isomerized pinene, pinene, dipentene, terpinene, terpinolene, limonene,turpentine, a terpene cut of fraction, and various other terpenes.Commercially available resins of the terpene type include the Zonarezterpene B-series and 7000 series from Arizona Chemical. Also includedare the rosin esters with acid numbers above 5 such as the Zonatacresins from Arizona Chemical. Particularly useful materials are terpenemixtures containing a mixture of sulphate terpene, and at least 20% ofat least one other terpene selected from the group consisting of pinene,limonene, or dipentene.

These adhesive compositions can also be modified to increase the RBSPand reduce cold flow by including additives such as precipitated calciumcarbonates and silicas such as fumed silica. A suitable fumed silicacomes from Cabot Corp. as CABOSIL.

The present copolyester composition can be modified with random oralternating styrenic copolymers useful in the compositions of thisinvention and may be prepared by any of the several methods availablefor their synthesis. For example, the copolymers may be obtained bysolution copolymerization directly from the respective monomers by theincremental additions of the more reactive monomer as taught by U.S.Pat. No. 2,971,939 or by a continuous recycle polymerization processdescribed in U.S. Pat. Nos. 2,769,804 and 2,989,517. Suitablecommercially available random or alternating copolymers include the"Dylark" styrene/maleic anhydride copolymers. Suitable blockedcopolymers for example from Shell Chemical, include Kraton FG-1901X orKraton FG-1921X linear styrene ethylene-1-butene styrene blockedcopolymers. In formulating adhesives or sealants for use herein, theblocked copolymers should be used of 5-20%, preferably 7-12%.

Modified polyolefins suitable for use in the present invention areprepared by reacting a polyolefin with unsaturated polycarboxylic acid,anhydride or esters thereof, such as maleic anhydride. In formulatingadhesive or sealants for use herein the modified polyolefins should beused in low amounts from 3-15% preferably 5-9%. These modifiedpolyolefins can enhance heat resistance of the composition.

The adhesive composition of this invention can be prepared using one ormore modifiers to the branched copolyester, by blending with thepolyester at melt temperatures of 177°-200° C. and mixing until ahomogeneous mixture is obtained. A cowles stirrer provides effectivemixing for these preparations.

The following examples are intended to illustrate the present inventionbut are not intended to limit the reasonable scope thereof.

EXAMPLES

In the following examples GEL Permeation Chromatography (GPC) is usedfor determination of the molecular weight distribution averages: Mw, Mn,Mw/Mn (polydispersity), and Mz.

In the following examples the Peel Adhesion Failure Temperature wasdetermined according to the following procedure to find the 180° peelingtension fail. This is determined by subjecting a specimen to acontinuous dead weight loading of 100 grams per inch (2.54 cm) of bondwidth for 10 minutes at a given temperature.

The adhesive is laminated onto 30 pound (13.6 kg) kraft paper to athickness of 1 mil (2.54×10⁻³ cm) and a width of 1.5 inches (3.8 cm).Another section of kraft paper is placed on top of the adhesivelaminate. The test specimen is heat sealed at 122° C. at 25 psi (0.17kpa) for 0.2 seconds. Three specimens are prepared. The bonded peelspecimens must condition overnight in a laboratory at 23° C. at 50%humidity before testing. The oven temperature is set at 14° C., thethree specimens are placed therein, and a 100 gram weight is attached toeach. The specimens are conditioned in the oven for 10 minutes, and thetemperature is then raised 4° C. at 10 minute intervals. The PeelAdhesion Failure Temperature is the temperature in degrees C. at failure(3 test average).

Example 1 Preparation and Testing of Branched Polyester

Control:

A 1000 mL round bottom flask equipped with a ground-glass head, agitatorshaft, nitrogen inlet, and a sidearm was charged with 139.4 grams (0.84mole) of isophthalic acid, 23.4 grams (0.16 mole) adipic acid, 95.4grams (0.90 mole) diethylene glycol, 31.2 grams (0.30 mole) neopentylglycol, 6.7 grams (0.05 mole) trimethylol propane, 10.0 grams (0.01mole) of poly(ethylene glycol), MW=1000, and 1.05 mL of a 1.46% (w/v)solution of titanium isopropoxide in n-butanol. The flask was purgedwith nitrogen and immersed in a Belmont metal bath at 200° C. for 90minutes and 220° C. for an additional 90 minutes under a slow nitrogensweep with sufficient agitation. After elevating the temperature to 280°C. a vacuum <=0.5 mm was installed 11 minutes to perform thepolycondensation. The vacuum was then displaced with a nitrogenatmosphere and the polymer was allowed to cool after removing the flaskfrom the metal bath. An inherent viscosity of 0.371 dL/g was determinedfor the recovered polymer according to ASTM D3835-79 and a glasstransition temperature of 3° C. was obtained from thermal analysis byDSC. The polymer was clear and amorphous. Molecular weights asdetermined by GPC were: Mn=10,400, Mw=32,250, and Mz=104,150. Theproperties of this resin are illustrated in Table 1. This sample whenplaced in tap water, pH approximately equal to 8, was insoluble andwould not be suitable for application as a repulpable adhesive.

Example 2 Preparation of Branched Water-Dispersible Polyester

A 1000 mL round bottom flask equipped with a ground-glass head, agitatorshaft, nitrogen inlet, and a sidearm was charged with 192.0 grams (1.15moles) of isophthalic acid, 35.1 grams (0.24 mole) adipic acid, 31.1grams (0.105 mole) dimethyl-5-sodiosulfoisophthalate, 143.1 grams (1.35mole) diethylene glycol, 46.8 grams (0.45 mole) neopentyl glycol, 10.05grams (0.075 mole) trimethylol propane, 30.0 grams (0.03 mole) ofpoly(ethylene glycol), MW=1000, and 1.67 mL of a 1.46% (w/v) solution oftitanium isopropoxide in n-butanol. The flask was purged with nitrogenand immersed in a Belmont metal bath at 200° C. for 90 minutes and 220°C. for an additional 90 minutes under a slow nitrogen sweep withsufficient agitation. After elevating the temperature to 280° C. avacuum <=0.5 mm was installed for 15 minutes to perform thepolycondensation. The vacuum was then displaced with a nitrogenatmosphere and the polymer was allowed to cool after removing the flaskfrom the metal bath. An inherent viscosity of 0.258 dL/g was determinedfor the recovered polymer according to ASTM D3835-79 and a glasstransition temperature of 9° C. was obtained from thermal analysis byDSC. The clear polymer was stabilized with 0.3 grams of Irganox 1010.Molecular weights as determined by GPC were: Mn=6,500, Mw=13,200, andMz=20,800. The properties of this resin are illustrated in Table 1.

Example 3 Preparation of Branched Water-Dispersible Polyester

A 1000 mL round bottom flask equipped with a ground-glass head, agitatorshaft, nitrogen inlet, and a sidearm was charged with 184.0 grams (0.92moles) of dimethyl cyclohexanedicarboxylate, 23.7 grams (0.24 mole)dimethyl-5-sodiosulfoisophthalate, 95.4 grams (0.90 mole) diethyleneglycol, 31.2 grams (0.30 mole) neopentyl glycol, 6.70 grams (0.05 mole)trimethylol propane, and 1.17 mL of a 1.46% (w/v) solution of titaniumisopropoxide in n-butanol. The flask was purged with nitrogen andimmersed in a Belmont metal bath at 200° C. for 90 minutes and 220° C.for an additional 90 minutes under a slow nitrogen sweep with sufficientagitation. After elevating the temperature to 280° C. a vacuum <=0.5 mmwas installed for 10 minutes to perform the polycondensation. The vacuumwas then displaced with a nitrogen atmosphere and the polymer wasallowed to cool after removing the flask from the metal bath. Aninherent viscosity of 0.210 dL/g was determined for the recoveredpolymer according to ASTM D3835-79 and a glass transition temperature of-4° C. was obtained from thermal analysis by DSC. The polymer was clearand nearly colorless. Molecular weights as determined by GPC were:Mn=5,800, Mw=10,400, and Mz=15,500. The properties of this resin areillustrated in Table 1.

Example 4 Preparation of Branched Water-Dispersible Polyester

A 1000 mL round bottom flask equipped with a ground-glass head, agitatorshaft, nitrogen inlet, and a sidearm was charged with 128.0 grams (0.77mole) of isophthalic acid, 23.4 grams (0.16 mole) adipic acid, 23.7grams (0.08 mole) dimethyl-5-sodiosulfoisophthalate, 95.4 grams (0.90mole) diethylene glycol, 31.2 grams (0.30 mole) neopentyl glycol, 6.70grams (0.05 mole) trimethylol propane, 10.0 grams (0.01 mole) ofpoly(ethylene glycol), MW=1000, and 1.09 mL of a 1.46% (w/v) solution oftitanium isopropoxide in n-butanol. The flask was purged with nitrogenand immersed in a Belmont metal bath at 200° C. for 90 minutes and 220°C. for an additional 90 minutes under a slow nitrogen sweep withsufficient agitation. After elevating the temperature to 280° C. avacuum <=0.5 mm was installed for 10 minutes to perform thepolycondensation. The vacuum was then displaced with a nitrogenatmosphere and the polymer was allowed to cool after removing the flaskfrom the metal bath. An inherent viscosity of 0.226 dL/g was determinedfor the recovered polymer according to ASTM D3835-79 and a glasstransition temperature of 13° C. was obtained from thermal analysis byDSC. The clear polymer was stabilized with 0.3 grams of Irganox 1010.Molecular weights as determined by GPC were: Mn=7,300, Mw=14,000, andMz=22,600. The properties of this resin are illustrated in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    PROPERTIES OF ADHESIVE COMPOSITIONS                                                (a)  (b)    (c)       (d)         (e) (f)                                Example                                                                            Set Time                                                                           Viscosity @                                                                          Tensile Strength                                                                        Peel Adhesion   Ring and Ball                      No., (sec)                                                                              177° C. cps                                                                   (mpa) elongation %                                                                      Failure Temperature °C.                                                            Tg °C.                                                                     Softening Point                    __________________________________________________________________________                                               °C.                         1    7.0  4,120  --        34          3   70                                 2    6.1  3,840  .09 > 1200%                                                                             35          9   82                                 3    4.2  3,570  .03-.09 > 1200%                                                                         30          -13 82                                 4    3.6  4,630  1.0, 873% 40          13  90                                                  elongation                                                   __________________________________________________________________________     (a) TAPPI Symposium, Recyclable/Repulpable Hot Melts  A Summary, June         1990, by Michael J. Ambrosini                                                 (b) ASTM D3236 Test Method                                                    (c) ASTM 412 Test Method                                                      (d) Kraft to kraft bond                                                       (e) ASTM D3418                                                                (f) ASTM E28                                                             

Example 5 Repulpability Test (Neutral)*

Approximately 10 grams of each of the adhesives in Examples 2, 3 and 4were melted, dyed, and coated onto white bond copier paper to athickness of 1.5 to 3.0 mils (0.04 to 0.08 mm) with a wire wound rod.The coated paper was then cut to obtain a piece weighing 12 grams. Theweighed coated paper was then torn into 1" by 1" (2.54 cm by 2.54 cm)pieces and placed into approximately 1000 mL of tap water in the bowl ofa laboratory blender to obtain a solids to liquid consistency of ˜1.2%and soaked from 1 to 4 hours. The coated paper and water were agitatedat 500 rpm for 10 minutes, at 1,000 rpm for 10 minutes, and 1,500 rpmfor 10 minutes. Following agitation, a portion of the slurry was removedfrom the bowl and diluted to produce a 0.7% solids mixture. This mixturewas stirred for 30 seconds and quickly poured into a Buchner funnel thatcontains a 100 mesh polyester screen. A vacuum pump was attached for ashort interval until the water was evacuated from the funnel and ahandsheet was formed. The handsheet and screen were then removed fromthe funnel and excess water was blotted away with Watman 5 filter paper.The handsheet was then weighted and dried on a warm hot plate. The driedhandsheet was then inspected for "stickies" using both transmitted andreflected light.

All three examples were completely dispersible, in that during the hoursoak in a room temperature neutral solution all dyed coating samplescompletely separated from copy paper. During agitation, the solution wasfoamy and a sweet odor was noticed. No adhesive residue (stickies) wereon the hand sheet. Thus, there was complete repulpability. This testshowed that the compositions in Examples 2, 3 and 4 were highly waterdispersible and repulpable under neutral conditions.

Example 6 Repulpability in alkaline solution*

An alkaline solution was prepared by adding 6.2 g of NaOH pellets, 3 gof tetrasodium pyrophosphate (TSPP) and 0.6 ml of Triton x-100surfactant to 400 ml of H₂ O at room temperature. The solution waswarmed on a hot plate to 27° C. When the TSPP had dissolved, it wasdiluted to 1000 ml and adjusted to a pH of 9-12 with H₂ O or base. Thesolution was then brought to 85° C. and then 1"×1" (2.54×2.54 cm) piecesof coated paper from Examples 2, 3 and 4 prepared as in Example 5 wereadded as the solution was slowly stirred at the blend station. Whencoated paper began to de-fiber, the mixer speed was adjusted to give agentle rolling of slurry. Mixing was continued for 15-30 minutes. Afterdefibering for 15-30 minutes, slurry was diluted to 1000 ml and stirredthoroughly to assure a uniform suspension. The handsheet was formed asin Example 5. The degree of adhesive repulpability was evaluated as inExample 5.

All three examples were completely dispersible, in that dyed coatingsample began separating from the copy paper within 5 minutes of enteringthe heated (85° C.) alkaline solution. During the 30 minute agitationthe coating completely dispersed throughout solution. There was a paleorange color visible in handsheet; however, no adhesive residue(stickies) was on hand sheet. Thus, there was complete repulpability.The results indicate that Examples 2, 3 and 4 are repulpable underalkaline conditions.

Example 7 Dispersibility of Adhesive Coated Wood Pulp

Wood pulp (5 grams) taken from a Huggies brand diaper from KimberlyClark, was coated with 1.5 grams of the adhesive from Examples 2, 3 and4 at 350° F. (177° C.). The adhesive coated wood pulp was placed in oneliter of tap water (pH 7.9) at room temperature for one hour with handstirring approximately every 10 minutes. The slurry was poured through a600 mL Hirsch funnel pulled under vacuum at 25 psi until water iscompletely removed out of the funnel. The wood pulp remained in thefunnel without any sign of adhesive present in the funnel. All of theadhesive passed through the funnel into the container with the water.

Example 8 Solubility of Examples 2, 3, and 4

A one gram sample of each polyester from Examples 2, 3, and 4 was placedin tap water (pH 8.0), deionized water (pH 7.2) and two simulated bodyfluids. The first simulated body fluid containing 10 gms. sodiumchloride, 4 gms. ammonium carbonate, 1 gm disodium hydrogen phosphate,and 0.25 grams histidine monohydrochloride, dissolved in 1 liter ofdeionized water, with a final pH 8.0. The second simulated body fluidcontaining 10 grams sodium chloride, 1 gram lactic acid, and 1 gramdisodium hydrogen phosphate, and 0.25 gram histidinemonohydrogenchloride, dissolved in 1 liter deionized water, with a finalpH of 3.9.

Test Results

Examples 2, 3, and 4 dissolved in less than one hour immersion in tapwater and deionized water and remained insoluble in simulated body fluidsolution after 24 hours immersion.

The following examples 1B through 9B are examples of the adhesivecomposition according to the present invention that is a blend of twopolyesters. These examples were tested according to the test used in theprior examples except for Gel Permeation Chromatography (GPC) which useda polystyrene standard.

GPC is used for determination of the molecular weight distributionaverages: Mw, Mn, Mw/Mn (polydispersity), and Mz. Approximately 60milligrams of sample is weighed and dissolved in 20 ml. oftetrahydrofuran (THF) containing toluene (internal std.) at a level of0.3% (v/v). The sample is filtered (if necessary) and then run on theGPC system. The data system generates a report showing: (1x) themolecular weight distribution averages, (2x) a time slice report, and(3x) standard, purchased from Polymer Laboratories, covering a molecularweight range of 580 to 1,030,000. The mode of calibration is "Narrow MWStandard Peak Positions".

Example 1B Preparation of Linear Water-Dispersible Polyester Composition1

A 500-mL, round bottom flask equipped with a ground-glass head, anagitator shaft, nitrogen inlet, and a sidearm was charged with 73.87 g(0.445 mol) of isophthalic acid, 14.74 g (0.055 mol) of5-sodiosulfoisophthalic acid, 81 g (0.75 mol) of diethylene glycol, 0.19grams of titanium tetraisopropoxide and 0.847 g (0.0055 mol) of sodiumacetate tetrahydrate. The flask was immersed in a Belmont bath at 200°C. for two hours under a nitrogen sweep. Heating was stopped and thecopolyester was removed from the flask. The polymer had an inherentviscosity of 0.45 dL/g according to ASTM D3835-79 and a glass transitiontemperature of 29° C. as measured by differential scanning colorimetry(DSC) analysis. The polymer which was transparent and amorphous wasextruded and pelletized. The polymer had a weight average molecularweight (Mw) of 8,924 and a number average molecular weight (Mn) of 5,422by GPC using a polystyrene standard.

Example 2B Preparation of Branched Water-Dispersible PolyesterComposition 2

To a three-neck round-bottom flask equipped with a mechanical stirrer, astream partial condenser a Dean-Stark trap, and a water condenser werecharged the following reactants: neopentyl glycol (363.38 g, 3.49 m),5-sodiosulfoisophthalic acid (29.30 g, 0.109 m) and the catalyst, Fascat4100 (Atochem North America, Inc.) (0.56 g). The mixture was heated to150° C. and stirred under N₂ atmosphere and the temperature thengradually increased to 220° C. and the distillate (water) was collectedin the Dean-Stark trap until the mixture was clear (about 1 hr). Theacid number was determined to be close to zero, and the mixture wascooled to 150° C. The second stage reactants, trimethylolpropane (75.4g, 0.563 m), isophthalic acid (329.01 g, 1.98 m) and adipic acid (202.25g, 1.38 m) were then added. The temperature was gradually raised to 220°C. and the reaction continued for four more hours to yield a resin withan acid number of 3.6. The polymer had a weight average molecular weight(Mw) of 6,241, a number average molecular weight (Mn) of 1,740 and apolydispersity index of 3.6, determined by GPC using a polystyrenestandard.

Example 3B Preparation of a Water-Dispersible Hot-Melt Adhesive

A blend of the linear water-dispersible polyester polymer 1 prepared asin Example 1B (70 parts) by weight and the branched water-dispersiblepolyester polymer 2 of Example 2B (30 parts) by weight was prepared bycombining the two polymers and stirring at about 225° C. for 2 hours toproduce the adhesive composition. The composition had a Tg of about 11°C., a weight average molecular weight of 5,410, a number averagemolecular weight of 1,554, and a viscosity of 19,450 centipoise at 350°F. (175° C.) as determined on a Brookfield HV: II Viscometer. Theadhesive had a fast set time, as determined by a standard procedure(TAPPI Symposium, Recyclable/Repulpable Hot Melts--A Summary--U.S.A. andEurope, June, 1990, by Michael J. Ambrosini) on a corrugated kraftboardsubstrate, good lap sheer strength (ASTM D1002 Test Method) and goodtensile strength (ASTM 412 Test Method). The results are reported inTable 2. Into 100 ml of hot water (65°-80° C.) at a pH of 7.8, weremixed 0.5 grams of adhesive chips. Within 15 minutes under mildagitation the adhesive was completely dispersed in the water, forming amilky mixture. Repulpability results are in Tables 3 and 4.

Example 4B

An adhesive composition was prepared by blending 60 parts by weight ofthe linear water-dispersible polymer prepared as in Example 1B with 40parts by weight of the branched water-dispersible polyester of Example2B and the properties of the polymer and the polymer and adhesiveproperties determined as in Example 3B above. The adhesive propertiesare reported in Table 2. The adhesive chips were dispersed in hot wateras in Example 3B within 15 minutes. The adhesive had good repulpingproperties (see Tables 2 and 3), a Tg of about 8.4° C. a weight averagemolecular weight of 5,272, a number average molecular weight of 1,563and a viscosity of 17,400 centipoise at 350° F. (175° C.).

Example 5B

An adhesive composition was prepared by blending 40 parts by weight ofthe linear water-dispersible polymer prepared as in Example 1B with 60parts by weight of the branched water-dispersible polyester of Example2B and the properties of the adhesive composition determined as inExample 3B. The adhesive properties are reported in Table 2. Theadhesive chips were dispersed in hot water as in Example 3B within 15minutes. The adhesive had good repulping properties (see Tables 3 and4), a Tg of 4.2° C. a weight average molecular weight of 7,622, a numberaverage molecular weight of 1,715 and a viscosity of 2,500 centipoise at350° F. (175° C.).

Example 6B

An adhesive composition was prepared by blending 30 parts by weight ofthe linear water-dispersible polyester prepared as in Example 1B with 70parts by weight of the branched water-dispersible polyester of Example2B and the properties of the adhesive composition determined as inExample 3B. The adhesive properties are reported in Table 2. Theadhesive chips were attempted to be dispersed in hot water as in Example3B, however, only partial dispersion occurred. The adhesive had marginalrepulping properties (see Tables 3 and 4), a Tg of 4.4° C., a weightaverage molecular weight of 7,316, a number average molecular weight of1,831 and a viscosity of 2,490 centipoise at 350° F.

                  TABLE 2                                                         ______________________________________                                        PROPERTIES OF ADHESIVE COMPOSITIONS                                                   (a)     (b)      (c)     (d)                                                  Set     Lap      Tensile Peel Adhesion                                Example Time    Shear    Strength                                                                              Failure                                      No.     (sec)   (mpa)    (mpa)   Temperature °C.                       ______________________________________                                        3B      1.7     8.6      2.9     43                                           4B      1.4     1.3      1.4     43                                           5B      1.8     4.3      .3      30                                           6B      3.6     4.3      .1      --                                           ______________________________________                                         (a) TAPPI Symposium, Recyclable/Repulpable Hot Melts  A Summary, June         1990, by Michael J. Ambrosini                                                 (b) ASTM D1002 Test Method                                                    (c) ASTM 412 Test Method                                                      (d) Kraft to kraft bond                                                  

Example 7B Repulpability Test (Neutral)

Approximately 10 grams of each of the adhesives in Examples 3B, 4B, 5B,and 6B were melted, dyed, and coated onto white bond copier paper to athickness of 1.5 to 3.0 mils (0.04 to 0.08 mm) with a wire wound rod.The coated paper was then cut to obtain a piece weighing 12 grams. Theweighed coated paper was then torn into 1" by 1" (2.54 cm by 2.54 cm)pieces and placed into approximately 1000 mL of tap water in the bowl ofa laboratory blender to obtain a solids to liquid consistency of ˜1.2%and soaked from 1 to 4 hours. The coated paper and water were agitatedat 500 rpm for 10 minutes, at 1,000 rpm for 10 minutes, and 1,500 rpmfor 10 minutes. Following agitation, a portion of the slurry was removedfrom the bowl and diluted to produce a 0.7% solids mixture. This mixturewas stirred for 30 seconds and quickly poured into a Buchner funnel thatcontains a 100 mesh polyester screen. A vacuum pump was attached for ashort interval until the water was evacuated from the funnel and ahandsheet was formed. The handsheet and screen were then removed fromthe funnel and excess water was blotted away with Watman 5 filter paper.The handsheet was then weighted and dried on a warm hot plate. The driedhandsheet was then inspected for "stickies" using both transmitted andreflected light. The repulpability properties are reported in Table 3.This test showed that the adhesive of Example 3B is the most highlywater-dispersible.

                                      TABLE 3*                                    __________________________________________________________________________    Repulp Evaluations Unconditional (Neutral)                                    EXAMPLE 3B                                                                              EXAMPLE  EXAMPLE  EXAMPLE 6B                                        Completely                                                                              4B       5B       Not/Very Slightly                                 Dispersible                                                                             Partial  Partial  Dispersible                                       __________________________________________________________________________    Dispersion of                                                                           Material began to                                                                      Polymer began to                                                                       No dispersion of                                  material began                                                                          disperse from                                                                          disperse from                                                                          polymer from paper                                immediately upon                                                                        paper after 2                                                                          paper immediately                                                                      was seen during                                   exposure of coated                                                                      minutes in water.                                                                      on exposure to                                                                         soaking period of                                 paper to water,                                                                         Material was off                                                                       water. Nearly                                                                          1 hr.                                             producing a milky                                                                       the paper and into                                                                     complete disper-                                                                       HANDSHEET                                         solution. milky solution                                                                         sion after 20                                                                          Gummy residue noticed                             Appeared to be                                                                          after 30 minutes                                                                       minutes soaking.                                                                       in pulper after agitation.                        completely                                                                              in water. Ring of                                                                      Formed milky                                                                           Handsheet had sticky                              dispersed after 15                                                                      dispersed material                                                                     solution during                                                                        areas of polymer throughout.                      minutes of soaking                                                                      noticed at bottom                                                                      soaking. Difficult to remove                               in water with NO                                                                        of soaking beaker                                                                      HANDSHEET                                                                              handsheet from filter                             AGITATION.                                                                              after 1 hr.                                                                            Gummy residue                                                                          screen after handsheet                            HANDSHEET HANDSHEET                                                                              noticed in pulper                                                                      formed. Some sticky                               Very little                                                                             Gummy residue                                                                          after agitation.                                                                       polymer remained on screen.                       evidence of                                                                             noticed in pulping                                                                     Undispersed                                                adhesive remaining                                                                      vessel following                                                                       polymer and                                                in handsheet.                                                                           agitation. Some                                                                        undefibered paper                                                    visible adhesive                                                                       were noticed in                                                      specks noticed in                                                                      handsheet                                                            handsheet.                                                          __________________________________________________________________________     *Tappi, 1993, Hot Melt Symposium Procedure, Barrett                      

Example 8B Repulpability in alkaline solution

An alkaline solution was prepared by adding 6.2 g of NaOH pellets, 3 gof tetrasodium pyrophosphate (TSPP) and 0.6 ml of Triton x-100surfactant to 400 ml of H₂ O at room temperature. The solution waswarmed on a hot plate to 27° C. When the TSPP had dissolved, it wasdiluted to 1000 ml and adjusted to a pH of 9-12 with H₂ O or base. Thesolution was then brought to 85° C. and then 1"×1" (2.54×2.54 cm) piecesof coated paper prepared as in Example 7B were added as the solution wasslowly stirred at the blend station. When coated paper began to defiber,the mixer speed was adjusted to give a gentle rolling of slurry. Mixingwas continued for 15-30 minutes. After defibering for 15-30 minutes,slurry was diluted to 1000 ml and stirred thoroughly to assure a uniformsuspension. The handsheet was formed as in Example 7B. The degree ofadhesive repulpability was evaluated as in Example 7B. The results arereported in Table 4.

                                      TABLE 4*                                    __________________________________________________________________________    Repulp Evaluations Alkaline (pH = 10.6)                                       EXAMPLE 3B  EXAMPLE 4B EXAMPLE 5B                                                                              EXAMPLE 6B                                   Completely Dispersible                                                                    Complete Dispersion                                                                      Partial   Partial                                      __________________________________________________________________________    Dispersion began                                                                          Dispersion began                                                                         Gummy residue                                                                           Some dispersion                              immediately upon                                                                          immediately on                                                                           noticed in pulper                                                                       before agitation.                            exposure to alkaline                                                                      exposure of coated                                                                       following agitation                                                                     Thick "pudding like"                         solution. Final                                                                           paper to alkaline                                                                        AND on filtration                                                                       residue produced                             handsheet appeared                                                                        solution. No                                                                             screen after                                                                            during alkaline                              free of dye and                                                                           adhesive apparent in                                                                     formation of                                                                            agitation. Dried                             adhesive.   handsheet. handsheet.                                                                              "circles" of residue                                                          were seen on filter side                                                      of handsheet. Handsheet                                                       difficult to remove                                                           from filter screen.                          __________________________________________________________________________     *Tappi, 1993, Hot Melt Symposium Procedure, Barrett                      

The above results show that adhesive prepared in Example 3B is bestfollowed by Example 4B. Although the adhesive from Examples 5B and 6Bwere only partially repulped in alkaline solution, this is significantlyimproved over conventional hot melt adhesives.

Example 9B Dispersibility of Adhesive Coated Wood Pulp

Wood pulp (5 grams) taken from a Huggies brand diaper from KimberlyClark, was coated with 1.5 grams of the adhesive from Example 5B at 350°F. (177° C.). The adhesive coated wood pulp was placed in one liter oftap water (pH 7.9) at room temperature for one hour with hand stirringapproximately every 10 minutes. The slurry was poured through a 600 mLHirsch funnel pulled under vacuum at 25 psi until water is completelyremoved out of the funnel. The wood pulp remained in the funnel withoutany sign of adhesive present in the funnel. All of the adhesive passedthrough the funnel into the container with the water.

We claim:
 1. A water-dispersible adhesive composition according to thepresent invention comprising a branched water-dispersible polyestercomposition made of the moieties of reaction products;(I) at least onedifunctional dicarboxylic acid which is not a sulfomonomer; (II) about 2to 15 mol percent, based on the total of all acid, hydroxyl and aminoequivalence, of residues of at least one difunctional sulfomonomercontaining at least one sulfonate group bonded to an aromatic ringwherein the functional groups are hydroxyl, carboxyl, or amino; (III) atleast one diol or a mixture of a diol and a diamine comprising:(A) about0.1 to 85 mol percent, based on the total mol percent of diol moietiesor diol and diamine moieties, of a diol or diamine having the formulaH(--OCH₂ CH₂ --)_(n) OH and HRN(.paren open-st.CH₂ CH₂ O.parenclose-st.)_(n) NHR wherein n is 2 to about 20 and R is hydrogen or C₁-C₆ alkyl provided that the mol percent of such moieties is inverselyproportional to the value of n; (B) about 0.1 to about 15 mol percent,based on the total mol percent of diol moieties or diol and diaminemoieties, of moieties of a poly(ethylene glycol) having the formulaH(--OCH₂ CH₂ --)_(n) OH wherein n is 2 to about 500, provided that themol percent of such moieties is inversely proportional to the value ofn; and (C) 0 to no greater than about 99 mol percent of the diolcomponent or diol and diamine mixture being selected from the groupconsisting of a glycol and a mixture of glycol and diamine having two--NRH groups, the glycol containing two --C(R¹)₂ --OH groups wherein R¹in the reactant is a hydrogen atom, an alkyl of 1 to 5 carbon atoms, oran aryl group of 6 to 10 carbon atoms; (IV) 0 to about 40 mol % of adifunctional monomer reactant selected from the group consisting ofhydroxycarboxylic acids having one --C(R--)₂ --OH group, aminocarboxylicacids having one --NRH group, aminoalkanols having one --C(R--)₂ OHgroup and one --NRH group and mixtures of said difunctional reactantswherein R in the reactant is hydrogen or an alkyl group of 1 to 6 carbonatoms; and (V) about 0.1 to 40 mol % of a multifunctional reactantcontaining at least three functional groups selected from the groupconsisting of hydroxyl, carboxyl, amino, and mixtures thereof; thepolymer containing substantially equal mol proportions of acidequivalents (100 mol %) and diol or diol and diamine equivalents (100mol %) wherein at least 20 weight percent of the groups linking themoieties of the monomeric units are ester linkages and wherein theinherent viscosity is at least 0.2 dL/g measured in a 60/40 parts byweight solution of phenol/tetrachloroethane at 25° C. and at aconcentration of about 0.25 g of polymer in 100 ml of the solvent, theglass transition temperature T_(g) is no greater than 20° C., and thering and ball softening point (RBSP) is at least 70° C.
 2. Thecomposition according to claim 1 wherein said difunctional sulfomonomerof (II) is in a concentration of about 6 to 10 mol percent.
 3. Thecomposition according to claim 1 wherein the moieties of (A) in the diolor mixture of diol and diamine are in a concentration of about 20 to 80mol percent and the moieties of (A) are selected from the groupconsisting of diethylene glycol, triethylene glycol and mixturesthereof.
 4. The composition according to claim 1 wherein the component(A) and (B) of (III) are different moieties and the moieties of (A) areselected from the group consisting of diethylene glycol, triethyleneglycol, and mixtures thereof and the moieties of (B) are in aconcentration of about 0.1 to 5 mol percent and are selected frompoly(ethylene glycols) wherein n is 5 to
 50. 5. The compositionaccording to claim 4 wherein the moieties of (B) are present at aconcentration of about 1 to 5 mol percent and n is 10 to
 30. 6. Thecomposition according to claim 1 wherein the moieties of component (C)are present in a concentration of about 30 to 70 mol percent and areselected from the group consisting of neopentyl glycol, ethylene glycol,1,3 propane diol, 1,4 butane diol, 1,6 hexane diol and cyclohexanedimethanol.
 7. The composition according to claim 1 wherein the moietiesof (V) are present in a concentration of about 0.1 to 20 mol percent. 8.The composition according to claim 7 wherein the moieties of (V) arepresent in a concentration of about 2 to 6 mol percent.
 9. Thecomposition according to claim 1 wherein at least 90 weight percent ofthe groups linking the moieties of the monomeric units are esterlinkages.
 10. The composition according to claim 1 wherein the numberaverage molecular weight of the polyester composition is between 3000and
 10000. 11. The composition according to claim 1 wherein the T_(g) isbetween 4° and -20° C.
 12. The composition according to claim 1 whereinthe T_(g) is less than 0° C.
 13. The composition according to claim 1wherein the ring and ball softening point of the composition is 80° to100° C.
 14. The composition according to claim 1 further comprising anadditional component selected from the group consisting of plasticizers,tackifiers, resins, elastomers, and low molecular weight polyolefins.